Cleaning and disinfection 40 inorganic and organic acids · sequestering agents For the majority of food processing operations it may be necessary, therefore employ a number of cleaning products, for specific operations. This requirement must be balanced by the desire to keep the range of cleaning chemicals on site to a minimum so as to reduce the risk of using the wrong product, to simplify the b of the safety officer and to allow chemical purchase to be based more on the economics of bulk quantities. The range of chemicals and their purposes is well documented(Anon. 1991, Elliot 1980, ICMSF 1980, 1988, Hayes 1985, Holah 1991, Koopal 1985, Russell et al. 1982)and only an overview of the principles is given here. Water is the base ingredient of allwet cleaning systems and must be of table quality. Water provides the cheapest readily available transport medium for rinsing and dispersing soils, has dissolving powers to remove ionic-soluble compounds such as salts and sugars, will help emulsify fats at temperatures above their melting point, and, in high-pressure cleaning, can be used as an abrasive agent. On its own, however, water is a poor wetting agent and cannot dissolve non-ionic compounds Organic surfactants(surface-active or wetting agents)are amphipolar and are omposed of a long non-polar(hydrophobic or lyophilic) chain or tail and a polar(hydrophilic or lyophobic) head. Surfactants are classified as anionic (including the traditional soaps), cationic, or non-ionic, depending on their ionic charge in solution, with anionics and non-ionics being the most common Amphipolar molecules aid cleaning by reducing the surface tension of water and by emulsification of fats. If a surfactant is added to a drop of water on a surface the polar heads disrupt the waters hydrogen bonding and so reduce the surface tension of the water and allow the drop to collapse andwet' the surface Increased wettability leads to enhanced penetration into soils and surface irregularities and hence aids cleaning action. Fats and oils are emulsified as the hydrophilic heads of the surfactant molecules dissolve in the water whilst the hydrophobic end dissolves in the fat. If the fat is surface-bound, the forces acting on the fat/water interface are such that the fat particle will form a sphere(to obtain the lowest surface area for its given volume) causing the fat deposit to roll-up' and detach itself from the surface. lkalis are useful cleaning agents as they are cheap, break down proteins through the action of hydroxyl ions, saponify fats and, at higher concentrations, may be bactericidal. Strong alkalis, usually sodium hydroxide(or caustic soda) exhibit a high degree of saponification and protein disruption, though they are corrosive and hazardous to operatives. Correspondingly, weak alkalis are less hazardous but also less effective. Alkaline detergents may be chlorinated to aid the removal of proteinaceous deposits, but chlorine at alkaline ph is not an effective biocide. The main disadvantages of alkalis are their potential to precipitate hard water ions, the formation of scums with soaps, and their poor disability• inorganic and organic acids • sequestering agents. For the majority of food processing operations it may be necessary, therefore, to employ a number of cleaning products, for specific operations. This requirement must be balanced by the desire to keep the range of cleaning chemicals on site to a minimum so as to reduce the risk of using the wrong product, to simplify the job of the safety officer and to allow chemical purchase to be based more on the economics of bulk quantities. The range of chemicals and their purposes is well documented (Anon. 1991, Elliot 1980, ICMSF 1980, 1988, Hayes 1985, Holah 1991, Koopal 1985, Russell et al. 1982) and only an overview of the principles is given here. Water is the base ingredient of all ‘wet’ cleaning systems and must be of potable quality. Water provides the cheapest readily available transport medium for rinsing and dispersing soils, has dissolving powers to remove ionic-soluble compounds such as salts and sugars, will help emulsify fats at temperatures above their melting point, and, in high-pressure cleaning, can be used as an abrasive agent. On its own, however, water is a poor ‘wetting’ agent and cannot dissolve non-ionic compounds. Organic surfactants (surface-active or wetting agents) are amphipolar and are composed of a long non-polar (hydrophobic or lyophilic) chain or tail and a polar (hydrophilic or lyophobic) head. Surfactants are classified as anionic (including the traditional soaps), cationic, or non-ionic, depending on their ionic charge in solution, with anionics and non-ionics being the most common. Amphipolar molecules aid cleaning by reducing the surface tension of water and by emulsification of fats. If a surfactant is added to a drop of water on a surface, the polar heads disrupt the water’s hydrogen bonding and so reduce the surface tension of the water and allow the drop to collapse and ‘wet’ the surface. Increased wettability leads to enhanced penetration into soils and surface irregularities and hence aids cleaning action. Fats and oils are emulsified as the hydrophilic heads of the surfactant molecules dissolve in the water whilst the hydrophobic end dissolves in the fat. If the fat is surface-bound, the forces acting on the fat/water interface are such that the fat particle will form a sphere (to obtain the lowest surface area for its given volume) causing the fat deposit to ‘roll-up’ and detach itself from the surface. Alkalis are useful cleaning agents as they are cheap, break down proteins through the action of hydroxyl ions, saponify fats and, at higher concentrations, may be bactericidal. Strong alkalis, usually sodium hydroxide (or caustic soda), exhibit a high degree of saponification and protein disruption, though they are corrosive and hazardous to operatives. Correspondingly, weak alkalis are less hazardous but also less effective. Alkaline detergents may be chlorinated to aid the removal of proteinaceous deposits, but chlorine at alkaline pH is not an effective biocide. The main disadvantages of alkalis are their potential to precipitate hard water ions, the formation of scums with soaps, and their poor rinsability. Cleaning and disinfection 403